Levitation is the process by which an object is suspended without physical contact. There are a number of types of levitation, including static levitation in the absence of motion of the suspended object, as well as dynamic levitation in which the suspended object undergoes some form of movement, such as rotational or translational movement.
Levitation can be achieved by applying a levitation force between an electromagnetic device and one or more magnetic materials, such as paramagnetic materials, diamagnetic materials, or superconducting materials. Dynamic levitation forces and other forces, such as alignment forces, can improve the efficiency and speed of the transportation of materials and people (e.g., via levitating trains or vehicles).
Conventional levitation systems can employ a moving magnetic array translating above immobile inductive elements. U.S. Pat. Nos. 5,722,326, 6,629,503, 6,633,217, 6,664,880, 6,758,146, 7,096,794, and 7,478,598 disclose one such system referred to as “Inductrack.” One drawback to the Inductrack system is that the magnetic arrays in this system induce favorable and disfavorable directions of current flow in the inductive elements. Current that flows in the disfavorable direction produces magnetic forces that counteract levitation forces. This is especially the case at low translational speeds. Accordingly, there remains a need for improved levitational systems.